How do I wash urine soaked towels?

Rinse them out, soak overnight in a bucket or tub of white vinegar and water. In the morning, launder as usual. When you take them out of the washer, give them a sniff. If not clean, rewash again.

Vinegar in wash

I'd rinse them really well outside first, soak them in vinegar water overnight, rinse again, and then wash. Good luck!

I would soak them in vinegar and dish soap in a bucket outside and rinse really well with the hose, then try to launder them.

If they are white- just use your regular laundry soap with a cup of bleach added. IN a healthy person (or dog) urine is sterile and water soluble.